13. Prevnar 13

Prevnar 13
Prevnar 13 isn't expected to lose patent protection until 2023. (Pfizer)

Prevnar 13
Company: Pfizer
2019 sales: $5.95 billion
Projected 2026 sales: $7.06 billion
Projected CAGR: +2%
Used for: pneumococcal pneumonia

As Pfizer offloads its generic Upjohn unit in a merger with Mylan, the drugmaker will lean on its blockbuster stalwarts as it moves into the next phase. One of those longtime top-sellers, pneumonia vaccine Prevnar 13, could be in for an even brighter future with years of market exclusivity ahead. 

Prevnar hit $5.95 billion in sales in 2019, making it Pfizer's best-selling solo medicine—unlike blood thinner Eliquis, which is co-marketed with Bristol Myers Squibb. In 2026, the year Prevnar loses patent protection, Evaluate Pharma forecasts the shot will rake in $7.06 billion in sales. 

With Prevnar's generic due date on the horizon, Pfizer is aggressively chasing an approval for a Prevnar follow-up. In the meantime, the drugmaker is hoping to lean on its older vaccine to get it over the hump of a possible generics unit spinoff. 

RELATED: Pfizer may look messy post-Upjohn spinoff, but better days could be ahead: analyst

13. Prevnar 13